Recent advances in semiconductor fabrication and processing has led to increased use of electroplating to deposit a variety of materials on semiconductor devices. Such materials include electroplated copper, nickel, and tin-silver alloys. Electroplating tin-silver alloys oftentimes leads to spurious metal buildup around the lip seal and cup regions of a substrate holder assembly (sometimes implemented as a clamshell assembly). This buildup, referred to as “lip seal plating” and/or “cup bottom plating,” depending on its location, may in some circumstances cause the seal between the substrate and lip seal to fail, resulting in contamination of inner portions of the clamshell assembly with potentially corrosive electroplating solution. Further, when either lip seal or cup bottom plating occurs, the uniformity and quality of plating on the wafer may be significantly decreased, and some sort of remedial action is generally necessary before more wafers can be plated effectively. There exists a need for a method of detecting normal operational excursions such as when lip seal plating and cup bottom plating are present, in order to avoid processing costly wafers under sub-standard plating conditions.